Intresting Idea but without any prompts you can just stuck in a few minutes at the start because of strange movement of character when you colide with up or down border you just thinking why? I press up but it doesn't move! So it will be better to do that it will be not invisible but some sort of thing that you can understand, That a border. Nice work and cool ijncreasing difficult I think you caught a good balance in skill of player and difficult of level, so it doesn't start to be boring. Good luck, and see you next time!